In a non-uniform memory access (NUMA) system, processors are typically distributed across books (such as boards or drawers), with each book including one or more processor connected memory local to the book. The books are interconnected by a network so that processors on one book can also access memory on other books.
Processors in NUMA systems can access local memory quickly and efficiently. However, when a processor needs to access remote memory on a different book, there is delay, which is known as latency. There are also bandwidth issues over the network that interconnects the books.